British Patent 967,127 (Nash), published on Aug. 19, 1964, discloses a film or web stretcher with a plurality of stretching cylinders arranged at different levels in a machine frame and cooperating with at least two press-on rollers. The press-on rollers are mounted on one end of a bellcrank, the other end of which is connected to a respective piston cylinder device, whereby the respective press-on roller can be tilted toward and away from the corresponding stretching cylinder. In such an arrangement the press-on force has, in addition to the desirable radial component, a substantial tangential component which is less desirable.
It is the purpose of the press-on roller or rollers to assure a bubble-free contact of the web or film with the respective stretching cylinder. Another purpose of the press-on roller or rollers is to increase the stretching forces that can be effectively introduced into the film or web being stretched. Still another purpose of the press-on roller or rollers is to avoid the formation of undulating longitudinal film or web edges. In other words, the cooperation of the stretching cylinder with the press-on roller shall make sure that the width of the stretched film or web is uniform through the length of the film or web.
The art leaves room for improvement, especially with regard to the above listed several different purposes of the press-on roller or rollers.